There is a growing desire to use point to multi-point services in wireless communication systems. In a point to multi-point service, one transmission point sends service data to multiple reception points simultaneously. Examples of point to multi-point services are multimedia broadcasts and multicast services.
One concept commonly employed in wireless systems is transmit diversity. In transmit diversity, multiple antenna elements are used to transmit the same service signals. The phases and amplitudes of the signal transmitted by each antenna are adjusted so that the overall transmission is focused towards a desired receiver. Other receivers in the system receive lesser amounts or no transmission energy from that service transmission. For point to point services, transmit diversity can be utilized to isolate users and, accordingly, increase the overall radio resource efficiency.
Although transmit diversity can be used to more efficiently use radio resources, in point to multi-point communications applying transmit diversity is problematic. Users receiving the point to multi-point communication may be so geographically disbursed that transmit diversity may degrade the received signal quality of some users. Additionally, the phase and amplitude information from multiple users needs to be processed. The information from the multiple users may be conflicting and difficult to coordinate. However, in certain situations, transmit diversity techniques could provide better radio resource utilization.
Accordingly, it is desirable to have techniques for using transmit diversity with point to multi-point services.